Bitumen membranes are used for waterproofing, soundproofing and covering a variety of surfaces. Such membranes are often used in the fields of civil engineering, construction and public works. More specific applications include roofing, sidewalk, bridge and walkway coverings, among others.
For roofing and other waterproofing applications, bitumen membranes are often installed by welding membranes together so as to produce an impermeable seal between overlapping adjacent membrane strips and/or by welding the membrane directly to the surface. This installation requires heat to melt and thus thermoweld the borders and/or contact surfaces of the bitumen membranes. The membranes are welded together along the borders to produce a number of membrane strips welded together to cover a surface, or are fully adhered to the surface.
To weld the bitumen membranes together, the membranes must be heated to a temperature at which the bitumen melts or becomes liquid enough so as to enable good thermowelded adherence between the membranes. Bitumen membranes can be heated along an overlapping border to thermoweld strips or on the underside to weld membranes to another surface.
Already known in the prior art are torches and other devices used for installing bitumen membrane coverings. Portable and heavier apparatuses are known in the art for layering bitumen membranes onto various surfaces.
For instance, a live flame torch may be used for installation procedures, especially those procedures favoring a portable apparatus. The live flame directly heats the bitumen to enable thermowelding. A disadvantage of using a live flame torch is that live flames generally increase hazards, including the possibility of fire and other safety issues. For example, during roofing installations of bitumen membranes using an exposed flame torch, the flame can inadvertently produce smoldering and fires in the roof substructure. Heating by exposed flames may also increase the risk of carbonization of the binder of the thermoweldable surface, which decreases the quality of the inter-membrane weld. It may also be difficult to have control of the level of heating when using an exposed live flame.
There are also certain hot air devices known in the thermowelding industry. Most of them have a main casing through which air is blown. The casing also contains a live flame, sometimes produced by a combustion chamber or a burner unit. The airflow passes through the burner unit, part of it adequately mixes with a fuel to produce a flame, the air is heated by the flame, and then expelled. The hot air devices known in the art produce the hot air in burner units of numerous and varied construction.
U.S. Pat. No. 6,155,321 (BINDSCHEDLER et al.) describes a machine, which incorporates at least one unit for the production of hot air for thermowelding covering strips. The construction of the hot air units of this machine may render it more difficult to downsize to smaller machines or torches, and presents certain disadvantages with regard to producing the hot air. More specifically, BINDSCHEDLER et al. describe their machine as including a blade burner to heat the air. The blades' rotation enables the proper air-fuel mixture to enable a flame to ignite. The air flows around and through the blades, mixing with the fuel, and is heated by the flame before being expelled.
U.S. Pat. No. 6,588,475 (SIMON JR. et al.) describes a hot air welder including a flame distribution assembly having one or more fuel outlets directed in the same direction as the airflow. The air passes around the fuel outlets and proceeds downstream, thereby mixing with the fuel to be ignited, and flowing in the same direction as the live flame.
U.S. Pat. No. 4,547,152 (SVENDSEN) describes a device for heating a bitumen layer, including a casing in which a burner gas nozzle is mounted. The air flows around the burner gas nozzle where it is heated by the flame and proceeds, heated, out the rear exit of the casing.
U.S. Pat. No. 2,396,968 (PHILLIPS JR.) describes a torch for thermowelding membranes. The torch device includes a casing including counter-current air passageways which lead to orifices or jets circumferentially spaced about the fuel nozzle and positioned upstream therefrom. The air thus flows into the combustion tube near the fuel nozzle to produce the flame and be heated.
French Patent Application No. 2,608,191 (BERNASCONI) describes a device for thermowelding bitumen membranes having a casing in which is arranged a fuel nozzle. A first portion of air flows around and past the fuel nozzle and into a chamber, which is open at both ends. The chamber walls are hollow and filled with a second portion of compressed air, which is expelled from an outlet in the same direction as the first portion airflow and flame. Both portions of air are then heated and expelled from an exit nozzle.
Other patents in the art describe hot air devices for thermowelding, but provide little or no indication of the combustion chamber required to produce the hot air. The devices known in the art of bitumen thermowelding by hot air production use combustion chamber constructions that give rise to a number of disadvantages. For instance, the known constructions result in devices that are expensive, complicated, awkward or inefficient.
Furthermore, certain factors involved in producing hot air for thermowelding bitumen membranes have not been adequately explored in the prior art. A few of such factors are the air-fuel mixture for producing the flame, the balance between static pressure and flowrate, and the prevention of the flame exiting the exit nozzle of the hot air device.
Also, it is an ever present goal to improve the portability or maneuverability of hot air devices for thermowelding membranes. Thus an efficient use of space and equipment is quite desirable.
The prior art shows devices in which the production of hot air to thermoweld bitumen membranes is plagued by numerous disadvantages. There is thus a need for a hot air device that overcomes at least some of the disadvantages mentioned above.